Getting Away From Garden Select

Okay, so I recently bought Oxbow Garden Select, and then learned (thank you @Amethyst) that it was bad for chins. However, my parents don't buy it.

They think it's okay. I've tried talking to them, but they say that unless my chinchilla, Pedro, either won't eat it or acts unhealthy after eating it, I can't switch. And I'm not gonna want him getting sick.

So, is there something that chinchillas can eat, but absolutely hate? If I put it in his food, maybe he'll stop eating it.